There is free image editing software that can be found on several popular free and trial software websites. They are very simple and let you crop, resize, convert, sharpen, etc. I use Faststone and Focusviewer. (Just make sure the software does not contain any spyware or unwanted add-ons like Chrome, browser toolbars, etc. They usually ask you during installation if you want these.) You might have used a thumbnail file instead of the image file.